Commodity products required in daily life become more and more diversified with the upgrading of living standard. Plastic products, such as mobile phone casings, MP3 player casings, plastic cups, and joysticks of game devices, are used everywhere in the world. To manufacture these products, plastic materials are heated and plasticized before being poured into molds. After the plastic materials are shaped and cooled down, the molds are opened and the products are thereby manufactured as desired. The plastic products often have barbed structures formed thereon. When a barbed structure is formed at a surface of a plastic product, a sideway core-pulling mechanism, which is often a sideway slidable block, must be used. When the mold is opened, the sideway core-pulling mechanism is driven by a guide mechanism to conduct a sideway movement for departing from the product. When the barbed structure is located at an intermediate portion of the plastic product, a special mold structure must be used to fulfill smooth molding and demolding operation at the time the mold is opened. However, the conventional mold for molding a plastic product having a barbed structure at an intermediate portion requires a large amount of space, consumes a large amount of materials, and requires high manufacturing costs.